This section requires the assessor to provide a score for the overall risk posed by an organism, taking into account previous answers to entry, establishment, spread and impact questions.
RESPONSE CONFIDENCE COMMENT
Summarise Entry
VERY LIKELY VERY HIGH
Gunnera tinctoria was historically introduced into Europe for ornamental purposes and there continues to be an active trade in this species both into and within Europe. However the exact extent of the trade into Europe is unknown.
Past and existing trade of this species has shown this species can survive transport as potted plants, seeds and rhizomes. It is likely for the species requirements to be catered for by the horticultural trader and subsequently by the gardener.
Due to the existing trade of Gunnera tinctoria in Europe, it being awarded the Award of Garden Merit in 2006 by the Royal Horticultural Society in Great Britain, and its use as an architectural species in a garden/park landscape, there remains a societal association to the plant. Therefore, it is very likely that Gunnera tinctoria will continue to enter into Europe through the pathway for horticultural/ornamental trade.
Summarise Establishment VERY LIKELY VERY HIGH Gunnera tinctoria has already become established in several European Member states and is invasive in parts of Ireland, United Kingdom and Portugal (São Miguel island, the Azores).
The species’ early growth and associated competitive superiority and reproductive traits, in addition to human activities that facilitate dispersal, aid in its establishment.
Gunnera tinctoria’s ability to reproduce sexually (seed) and asexually (vegetative) may allow it to survive eradication campaigns. The formation of a persistent soil seed bank may also allow the species to survive even longer-term eradication campaigns.
Summarise Spread
MODERATE MEDIUM
While Gunnera tinctoria can spread by natural means such as seed dispersal and rhizome spread, human aided spread is likely to be a more significant factor in Gunnera tinctoria extending its range. Those areas where the species is already recorded and which are climatically suitable and with suitable habitats, are at risk of invasion expansion and further spread of the species to new sites in the next 80 years.
Modelling results of Fennell et al. (2013) suggest that the areas occupied by this species in Ireland (and this could be representative of suitable areas elsewhere) could increase by 3-fold by 2100 in the absence of climate change. In the presence of climate change the figure could be 6-fold. For the number of individuals in invaded sites the figures could be a 5-fold increase in the absence of climate change and an over 17-fold increase with climate change.
Even if existing efforts to control the species are both sustained and expanded along with continued efforts to ascertain the most effective control/eradication methods, it is unlikely to significantly reduce further spread of the species. However, if control and eradication measures of existing populations combined with biosecurity measures (such as not using aggregate from infested quarries on road building or inappropriately discarding un-wanted Gunnera tinctoria plants) and trade restrictions on sale and import are implemented, then significant further spread would be reduced.
While the Atlantic and Macaronesia biogeographical regions are most suited to support establishment of this species in Europe, where Gunnera tinctoria has become invasive, hyper-oceanic climates prevail (Sheehy Skeffington and Hall, 2011; Osborne et al., 1991).
Thus, the invasive potential of this species may be restricted to these areas. These hyper-oceanic regions could be crudely described as: the north-west of the Iberian peninsula (both Portugal and Spain), coastline of Ireland, north and north-west of Scotland, south-west tip of England, a small area of north-south-west France and the Azores (Sheehy Skeffington and Hall, 2011).
Summarise Impact MODERATE MEDIUM The most significant impacts of Gunnera tinctoria are on biodiversity. Due to its large size and early growth shading, it significantly reduces the number of native species in
colonised areas and impacts on habitats by changes in the vegetation structure, and on the natural succession of native vegetation. The capacity for Gunnera tinctoria to alter the soil seed bank of resident communities significantly, indicate that invasion by Gunnera tinctoria can alter the transient and the more persistent component of the seed bank, with potential long-term implications on the composition of the native vegetation.
investigation on the extent and scale of the impacts, especially on habitats and species of conservation significance would be desirable.
Modelling results of Fennell et al. (2013) suggest that the areas occupied by this species in Ireland could increase by 3-fold by 2100 in the absence of climate change. In the presence of climate change the figure could be 6-fold. For the number of individuals in invaded sites, the figures could be a 5-fold increase in the absence of climate change and over 17-fold increase with climate change.
It is highly likely that similar impacts to those already experienced in invaded sites in Europe and as those modelled, would be expected to occur in areas suitable for establishment and invasion in Europe.
Existing and future projected costs are estimated to be major but these costs are
associated with cost of control/eradication. There is likely to be a moderate level of impact to ecosystem functioning and services (and associated costs) such as changes in water and biogeochemical cycles; increased erosion along watercourses and coastal areas; loss of land for agricultural use and, cost of action taken to combat soil and blocked drainage which could lead to potential for enhanced flooding, but this requires further research.
Further establishment and spread of the species could have a moderate impact on areas in Europe that fall within the hyper-oceanic regions and have suitable habitats and abiotic conditions. The hyper-oceanic areas of Europe where the species is already established and where future expansion and intentional introduction of the species is most likely, will primarily incur the larger economic, environmental and social impacts.
Conclusion of the risk assessment MODERATE MEDIUM While Gunnera tinctoria has a major impact on sites where it has invaded and such invasion is likely to intensify and spread in the future, to date, the sites of invasion tend to be species poor communities with the exception of São Miguel Island in the Azores.
Therefore, the overall conclusion is that Gunnera tinctoria poses as a MODERATE risk to Member states that have territory with a hyper-oceanic climate.
However, as there are few detailed studies on impacted sites, further investigation on the extent and scale of impacts on habitats and species of conservation significance would be desirable and may increase the level of risk. In the absence of this information, a MEDIUM level of confidence is given for the overall conclusion.
While ecosystem function and service impacts have been noted, there is a lack of information on the extent and scale of the impacts.
Gunnera tinctoria has been and continues to be traded into and within Europe for use as an ornamental plant and is spread by both natural and human-aided dispersal with
human-aided dispersal a more significant factor in it extending its range. Once
established, it can be very difficult to eradicate. Therefore, if control/eradication measures of existing populations combined with biosecurity measures and trade restrictions on sale and import are implemented, significant further introductions and spread would be reduced.
The inadvertent trade of Gunnera tinctoria as a result of mistaken identification with Gunnera manicata may also need to be considered as the two species are difficult to tell apart. This is of particular concern when seed is being traded.
Stage 2 - Detailed assessment: Section F – Additional questions
This section is used to gather information about the potential effects of climate change on the risk posed by an organism. It is also an opportunity for the risk assessor to highlight high priority research that could help improve the risk assessment.
N QUESTION RESPONSE CONFIDENCE JUSTIFICATION
6.01 What aspects of climate change, if any, are most likely to affect the risk assessment for this organism?
Increase in oceanic climate
LOW Predictions for climate change in north-western Europe suggest an overall increase in oceanicity (Crawford, 2000) which could further increase the suitability of the range area where Gunnera tinctoria could become establish and/or become invasive.
Expansion of its range could be favoured by projected increases in winter rainfall and summer temperatures (Gioria and Osborne 2009).
Modelling projections of Fennell et al. (2013) indicate that habitat availability may have a greater impact on spread than climate change.
However, habitat availability will also be influenced by climate change and impact on spread indirectly.
Modelling results of Fennell et al., 2013, suggest that the areas occupied by this species in Ireland (could be representative of suitable areas elsewhere) could increase by 3-fold by 2100 in the absence of climate change. In the presence of climate change the figure could be 6-fold. For the number of individuals the figures could be 5-fold in the absence of climate change and over 17-fold with climate change. This also indicates another important point that intensification of the invasion in areas already invaded as number of individuals increasing is greater
highlight high priority research that could help improve the risk assessment.
N QUESTION RESPONSE CONFIDENCE JUSTIFICATION
than the number of localities. Management therefore becomes more difficult in existing areas.
Extreme weather events are also associated features of climate change in Europe. One such extreme weather event in Ireland was the
exceptionally severe winter of 2009/2010, when such freezing temperatures had not been experienced since 1986. Sheehy
Skeffington and Hall (2011) found that the severe frosts of 2009/2010 kept the invasive population of Gunnera tinctoria in north west Connemara in check and noted that if these cease to occur regularly Gunnera tinctoria is likely to increase in its range.
A confidence level of LOW is given as how climate change predictions will affect species responses in the future can be difficult to be confident about, particularly in the absence of specific modelling for that species.
6.02 What is the likely timeframe for such changes?
80 years LOW
The likely timeframe for such changes is 80 years but noting that the predicted increasing frequency of milder, wetter winters are already being experienced in Ireland (winter 2009/2010 being an exception).
A confidence level of LOW is given as how climate change predictions will affect species responses and within what timeframe can be difficult to be confident about, particularly in the absence of specific modelling for Gunnera tinctoria beyond Ireland.
6.03 What aspects of the risk assessment are most likely to change as a result of
climate change Increased
It is likely that there would be an increase in areas suitable for the species to establish and become invasive. There could also be an increase in the intensity of the invasion with increased numbers of individuals. Therefore, the level of impact associated costs would also increase.
EPPO 2014, note that ‘its climatic potential range remains uncertain and could be wider considering the native distribution of the species in South America. The area of potential establishment would
nevertheless remain moderate. The species still has a medium for further spread but the uncertainty on this point remains high’.
6.04 If there is any research that would significantly strengthen confidence in the risk assessment, please note this here. If more than one research area is provided, please list in order of priority.
YES MODERATE As there are few detailed studies on impacted sites, further investigation on the extent and scale of impacts on habitats and species of conservation significance would be desirable better inform the level of risk and confidence.
Stage 2 - Detailed assessment: Section F – Additional questions
This section is used to gather information about the potential effects of climate change on the risk posed by an organism. It is also an opportunity for the risk assessor to highlight high priority research that could help improve the risk assessment.
N QUESTION RESPONSE CONFIDENCE JUSTIFICATION
An understanding of the actual ecosystem impacts is required. Much of the supposed effects on hydrology and nutrient cycling are still very speculative and such research is needed to provide a more rational/accurate risk assessment.
The possibility that birds may be a significant vector for spread also needs investigation as this would affect the spread potential of the species in Europe and possibly also as a pathway into Europe.
Research on whether there is hybridisation between Gunnera tinctoria and Gunnera manicata (or other Gunnera species) and if hybrids do occur, what is their invasive potential. This would affect the known distribution of Gunnera tinctoria whereby records may be of hybrids. If hybrids do occur, then the presence of Gunnera manicata (or other Gunnera species) both in trade and in the open environment would also have to be considered for trade restrictions and possible control.